Navigation system

Abstract

A vehicular navigation system includes: a current position detection unit for detecting the current position of the vehicle; an information storage unit for storing map information for conducting route searching and for providing route guidance; an input unit for inputting a destination and inputting instructions for executing a search of the map information for a route from the current position detected by the current position detection unit to the destination; an output unit for outputting information for route guidance; and a central processing unit for temporarily memorizing a route detected by the route search and for outputting a signal to the output unit to provide route guidance according to the memorized route. The central processing unit judges whether or not one information storage unit has been replaced by another and, when replaced, if the destination has not been reached, conducts another route search from the current position to the destination.

What is claimed is: 
     
       1. A navigation system for conducting route searching and for providing route guidance to a destination, said navigation system comprising: current position detection means for detecting a current position of a vehicle;   a replaceable information storage unit for storing map information;   destination input means for inputting the destination;   output means for outputting route guidance information for guiding travel; and   central processing means for executing the route search to determine a route to the destination based on the map information stored in said information storage unit, for obtaining route information for guidance along the route determined by the route search, for storing the retrieved route information, for outputting signals to the output unit for execution of route guidance for travel according to the determined route, for detecting replacement of said replaceable information storage unit by another information storage unit, for determining if route guidance to the destination has been completed and, in response to detection of the replacement of said replaceable information storage unit and a determination that guidance to the destination along the determined route has not been completed, for conducting a new route search to the destination based upon the map information in the another information storage unit.   
     
     
       2. A navigation system according to claim 1 wherein said replaceable information storage unit contains a program, wherein said central processing means includes an internal storage means for storing the program read from said replaceable information storage unit, and wherein said central processing means, responsive to replacement of the replaceable information storage unit with the another information storage unit containing a different program, reading and storing the different program in said internal storage means. 
     
     
       3. A navigation system according to claim 2 further comprising condition input means for inputting a search condition and wherein said central processing means executes the new route search based on the input search condition. 
     
     
       4. A navigation system according to claim 1 further comprising: an internal storage medium included within said central processing means;   condition input means for inputting a search condition for storage in said internal storage medium; and   wherein said new route search is executed by said central processing means based on the stored search condition.   
     
     
       5. A navigation system in which a route to an input destination is searched and route guidance is carried out following the searched route, said navigation system comprising: a plurality of map information storage means each containing at least one portion of stored map information for conducting route guidance following said route and external information of a plan-view shape and a three-dimensional shape of buildings and internal information relating to the buildings;   range information extracting means for extracting the geographical coordinate range of said map information from each of the plurality of the map information storage means;   current position detecting means for detecting the current position coordinates of a vehicle;   map information selecting means for selecting at least one of the plurality of map information storage means in which the current position coordinates detected by the current position detecting means is contained based upon the geographical coordinate range extracted by the range information extracting means from said plurality of the map information storage means; and   read/display means for reading said map information from said at least one map information storage means selected by said map information selecting means and displaying said map information.   
     
     
       6. A navigation system in which a route to an input destination is searched and route guidance is carried out following the searched route, said navigation system comprising: a plurality of map information storage means each containing at least one portion of stored map information with geographical coordinates for conducting route guidance following said route;   range information extracting means for extracting a geographical coordinate range of said map information from each of the plurality of the map information storage means;   use frequency accumulating means for accumulating a use frequency of each of said map information storage means;   map information selecting means for selecting one map information storage means of the plurality of map information storage means based upon a highest use frequency accumulated by said use frequency accumulating means; and   read/display means for reading said map information from said one map information storage means selected by said map information selecting means and displaying said map information.   
     
     
       7. A navigation system according to claim 6 wherein said map information selecting means conducts said selection when the power of the navigation system is turned on and when said map information storage means is loaded or replaced.